Invasive Lobular Carcinoma

Invasive lobular carcinoma (ILC) is the second most common type of invasive breast cancer, accounting for about 1 in 10 to 1 in 7 cases (10-15%) of all breast cancers. It begins in the milk-producing glands (lobules) of the breast and has spread into the surrounding breast tissue. Unlike other breast cancers, ILC often grows in a subtle, diffuse pattern.

What is Invasive Lobular Carcinoma?

Invasive lobular carcinoma (ILC) is a type of breast cancer that starts in the milk-producing glands (lobules) and spreads into nearby breast tissue. It is called "invasive" because the cancer cells have broken out of the lobule where they began. ILC is the second most common type of invasive breast cancer.

ILC accounts for about 1 in 10 to 1 in 7 cases (10-15%) of all invasive breast cancers. The cancer cells typically grow in a single-file line, which can make them harder to detect as a distinct lump during a physical exam or on imaging tests like mammograms. This growth pattern allows the cancer to spread more diffusely throughout the breast. Because ILC is "invasive," it means the cancer cells have the potential to spread beyond the breast to other parts of the body, a process called metastasis. Understanding this characteristic is important for diagnosis and treatment planning. While it originates in the lobules, its invasive nature means it requires careful monitoring and treatment to prevent or manage its spread.

Symptoms

Symptoms of invasive lobular carcinoma (ILC) are often subtle and may not include a distinct lump, making it different from other breast cancers. Instead, you might notice a thickening or fullness in part of your breast, changes in breast size or shape, or a newly inverted nipple. These changes can be hard to feel or see.

Unlike invasive ductal carcinoma, which often presents as a firm, distinct lump, ILC commonly causes more diffuse changes. You might feel an area of your breast that feels thicker or fuller than the surrounding tissue, or different from the other breast. This can be due to the cancer cells growing in a single-file line, spreading subtly through the breast tissue. Other possible symptoms include changes in the size or shape of your breast, such as one breast becoming larger or smaller. The skin over the breast might also show changes, like dimpling or puckering. A newly inverted nipple, where the nipple turns inward, can also be a sign. Because these symptoms can be subtle, it's important to pay attention to any persistent changes in your breasts and discuss them with a doctor.

Causes & risk factors

The exact cause of invasive lobular carcinoma (ILC) is not fully understood, but it involves genetic mutations that lead to uncontrolled cell growth. Several factors can increase your risk, including older age, being female, using postmenopausal hormone therapy, having a family history of breast cancer, and certain genetic mutations like CDH1.

ILC, like other cancers, develops when genetic mutations occur in breast cells, causing them to grow and divide abnormally. While these mutations can happen randomly, certain factors are known to increase the likelihood of developing ILC. The risk generally increases with age, with most diagnoses occurring after menopause. Key risk factors include being female, as ILC is much more common in women. Using combined estrogen and progestin hormone therapy after menopause is also linked to an increased risk. A family history of breast cancer, particularly ILC, can raise your risk. Additionally, specific genetic mutations, such as the CDH1 gene mutation, are strongly associated with ILC and hereditary diffuse gastric cancer syndrome. Other factors like alcohol consumption, obesity, and a history of certain benign breast conditions like lobular carcinoma in situ (LCIS) or atypical lobular hyperplasia can also increase risk.

How it's diagnosed

Diagnosing invasive lobular carcinoma (ILC) often begins with a physical exam and imaging tests. Mammograms can be challenging due to ILC's diffuse growth pattern, so ultrasound and magnetic resonance imaging (MRI) are often more effective. A definitive diagnosis is made through a biopsy, where a tissue sample is examined under a microscope.

During a physical exam, your doctor will check your breasts for any lumps, thickening, or other changes. Due to ILC's subtle growth pattern, it can be difficult to detect on a standard mammogram, sometimes appearing as only a subtle distortion or asymmetry rather than a clear mass. This means additional imaging is often necessary. Ultrasound and magnetic resonance imaging (MRI) are frequently used because they can provide clearer images of ILC. An MRI, in particular, is often more effective at identifying the extent of ILC within the breast. If an area of concern is found, a biopsy is performed. This involves taking a small tissue sample, usually with a core needle, which is then sent to a lab. A pathologist will examine the cells to confirm the presence of cancer, determine its type (ILC), and assess other important characteristics like hormone receptor status.

Treatment options

Treatment for invasive lobular carcinoma (ILC) is personalized based on the cancer's stage, characteristics, and your overall health. Common treatments include surgery to remove the tumor, radiation therapy, chemotherapy, and hormone therapy. Because most ILCs are hormone receptor-positive, hormone therapy is often a crucial part of the treatment plan.

Surgery is typically the first step in treating ILC. This may involve a lumpectomy, which removes only the cancerous tissue and a small margin of healthy tissue, or a mastectomy, which removes the entire breast. In some cases, lymph nodes in the armpit are also removed to check for cancer spread. After surgery, radiation therapy may be recommended, especially after a lumpectomy, to destroy any remaining cancer cells in the breast area. Systemic treatments, which affect the whole body, include chemotherapy, hormone therapy, and targeted therapy. Chemotherapy uses drugs to kill cancer cells throughout the body and may be used if the cancer has a high risk of recurrence or spread. Hormone therapy is very common for ILC because most ILCs are hormone receptor-positive, meaning their growth is fueled by hormones like estrogen. Medications like tamoxifen or aromatase inhibitors can block these hormones or reduce their levels. Targeted therapy may be an option if the cancer has specific genetic mutations or protein overexpression, though ILC is usually HER2-negative, meaning it often doesn't respond to HER2-targeted drugs.

Recovery & outlook

The recovery and outlook for invasive lobular carcinoma (ILC) depend on factors like the cancer's stage at diagnosis, its characteristics, and how well it responds to treatment. While ILC can be challenging to detect early due to its subtle growth, many people achieve successful outcomes. Long-term follow-up care is crucial, as ILC can sometimes recur many years after initial treatment.

After treatment, recovery involves healing from surgery and managing any side effects from radiation, chemotherapy, or hormone therapy. Your healthcare team will provide guidance on managing pain, fatigue, and other symptoms. Regular follow-up appointments are essential to monitor your health and check for any signs of recurrence. While the prognosis for ILC is generally good when caught early, its diffuse growth pattern can sometimes lead to diagnosis at a later stage compared to other breast cancers. It's also important to know that ILC has a tendency to recur, sometimes even many years after initial treatment. Therefore, long-term surveillance, which may include regular physical exams and imaging, is a critical part of ongoing care. Your doctor will discuss a personalized follow-up plan to help ensure the best possible long-term outcome.

When to see a doctor

You should see a doctor if you notice any new or persistent changes in your breasts. This includes feeling a new lump or thickening, observing changes in breast size or shape, nipple changes like inversion or discharge, or any dimpling or puckering of the skin. Prompt evaluation of these signs is important.

It is crucial to be aware of your breasts and report any unusual findings to your healthcare provider without delay. While many breast changes are not cancer, only a doctor can properly evaluate them. Do not wait to see if a symptom goes away on its own. Specific signs that warrant a doctor's visit include: a new lump or an area of thickening that feels different from the rest of your breast or the other breast; any changes in the size, shape, or contour of your breast; skin changes such as dimpling, puckering, redness, or scaling; a newly inverted nipple or any nipple discharge; or persistent breast pain that does not go away. Early detection of breast cancer, including ILC, can lead to more effective treatment and better outcomes.

Frequently asked questions

Is Invasive Lobular Carcinoma more aggressive than other breast cancers?

Invasive lobular carcinoma (ILC) is not necessarily more aggressive than other common types of breast cancer, but it can be more challenging to detect early. Its diffuse growth pattern often makes it harder to feel as a distinct lump or see on mammograms. ILC also has a tendency to recur many years after initial treatment, requiring long-term monitoring.

Why is ILC hard to find on a mammogram?

ILC is often difficult to detect on a mammogram because its cells tend to grow in a single-file line, spreading subtly through breast tissue rather than forming a dense, distinct mass. This diffuse growth can make it appear as only a subtle distortion or thickening, which can be easily missed. Other imaging tests like ultrasound and MRI are often more effective for ILC.

What is the CDH1 gene mutation and how is it related to ILC?

The CDH1 gene mutation is a genetic change that significantly increases the risk of developing invasive lobular carcinoma (ILC) and hereditary diffuse gastric cancer syndrome. If you have this mutation, your doctor may recommend increased surveillance for both breast and stomach cancers, and sometimes preventive surgeries.

Is hormone therapy always used for ILC?

Hormone therapy is a very common and often crucial treatment for ILC. This is because most invasive lobular carcinomas are hormone receptor-positive, meaning their growth is fueled by hormones like estrogen. Medications that block these hormones or reduce their levels are frequently prescribed for several years to help prevent recurrence.

Can men get Invasive Lobular Carcinoma?

While invasive lobular carcinoma (ILC) is much more common in women, men can rarely develop it. Male breast cancer accounts for a very small percentage of all breast cancers, and ILC is an even rarer subtype in men. The symptoms, diagnosis, and treatment principles are generally similar to those in women.

What is the main difference between Invasive Lobular Carcinoma (ILC) and Invasive Ductal Carcinoma (IDC)?

The main differences between ILC and invasive ductal carcinoma (IDC) lie in their origin and growth patterns. ILC starts in the milk-producing glands (lobules) and grows diffusely in single-file lines, often making it harder to detect. IDC, the most common type, starts in the milk ducts and usually forms a more distinct, palpable lump. ILC is also more frequently hormone receptor-positive and HER2-negative compared to IDC.

Sources

• MedlinePlus — Invasive Lobular Carcinoma
• Mayo Clinic — Invasive Lobular Carcinoma
• Cochrane Library — Invasive Lobular Carcinoma